JP7162247B2 - Receiving device and receiving method - Google Patents

Receiving device and receiving method Download PDF

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JP7162247B2
JP7162247B2 JP2018232285A JP2018232285A JP7162247B2 JP 7162247 B2 JP7162247 B2 JP 7162247B2 JP 2018232285 A JP2018232285 A JP 2018232285A JP 2018232285 A JP2018232285 A JP 2018232285A JP 7162247 B2 JP7162247 B2 JP 7162247B2
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和広 加藤
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Panasonic Intellectual Property Management Co Ltd
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04HBROADCAST COMMUNICATION
    • H04H40/00Arrangements specially adapted for receiving broadcast information
    • H04H40/18Arrangements characterised by circuits or components specially adapted for receiving
    • H04H40/27Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
    • H04H40/36Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving
    • H04H40/45Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving
    • H04H40/72Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving for noise suppression
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10LSPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/0208Noise filtering
    • G10L21/0216Noise filtering characterised by the method used for estimating noise
    • G10L21/0232Processing in the frequency domain
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10LSPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/0316Speech enhancement, e.g. noise reduction or echo cancellation by changing the amplitude
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10LSPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L25/00Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
    • G10L25/03Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the type of extracted parameters
    • G10L25/18Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the type of extracted parameters the extracted parameters being spectral information of each sub-band
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06Receivers
    • H04B1/10Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
    • H04B1/1036Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06Receivers
    • H04B1/16Circuits
    • H04B1/1646Circuits adapted for the reception of stereophonic signals
    • H04B1/1661Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels
    • H04B1/1669Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels of the demodulated composite stereo signal
    • H04B1/1676Reduction of noise by manipulation of the baseband composite stereophonic signal or the decoded left and right channels of the demodulated composite stereo signal of the sum or difference signal
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00Circuits for transducers, loudspeakers or microphones
    • H04R3/04Circuits for transducers, loudspeakers or microphones for correcting frequency response
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10LSPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L25/00Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
    • G10L25/48Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use
    • G10L25/51Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use for comparison or discrimination
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06Receivers
    • H04B1/10Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
    • H04B2001/1054Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal by changing bandwidth
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00Reducing energy consumption in communication networks
    • Y02D30/70Reducing energy consumption in communication networks in wireless communication networks

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Computational Linguistics (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
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  • Computer Networks & Wireless Communication (AREA)
  • Spectroscopy & Molecular Physics (AREA)
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Description

本開示は、FMの放送波等の無線信号を受信する受信装置及び受信方法に関する。 The present disclosure relates to a receiving device and a receiving method for receiving radio signals such as FM broadcast waves.

従来、FM放送等のラジオ放送を受信する受信装置においては、ノイズを低減させるために、受信信号を復調した音声信号の高域成分を減衰させるハイカット処理が行われる。このハイカット処理では、ノイズ成分だけでなく、音声信号の高域成分も減衰される。ラジオ放送を受信する際に、ハイカット処理により音声信号の高域成分が過剰に減衰されると、放送における音楽等の曲調まで変化してしまうことがある。 2. Description of the Related Art Conventionally, in a receiving apparatus that receives radio broadcasting such as FM broadcasting, high-cut processing is performed to attenuate high-frequency components of an audio signal obtained by demodulating a received signal in order to reduce noise. This high-cut processing attenuates not only noise components but also high-frequency components of the audio signal. When receiving a radio broadcast, if the high-frequency components of the audio signal are excessively attenuated by the high-cut processing, even the tone of the music in the broadcast may change.

例えば、特許文献1には、パルス性雑音検出回路からの出力信号に応じてオーディオ信号の低周波数域と高周波数域の再生を制限する技術が開示されている。 For example, Japanese Unexamined Patent Application Publication No. 2002-200000 discloses a technique for restricting reproduction of a low frequency range and a high frequency range of an audio signal according to an output signal from a pulse noise detection circuit.

実開昭63-85929号公報Japanese Utility Model Laid-Open No. 63-85929

ラジオ放送の受信信号から抽出された音声信号の高域成分は、ノイズの影響だけでなく、音声信号に元々含まれる情報、受信装置内部の熱雑音等の影響を受ける。このため、特許文献1に記載の従来技術のように、高域成分の減衰量を高域レベルの検出結果に応じて制御するものでは、元の音声信号の周波数特性に対して減衰量が適切に制御されない場合がある。この場合、ラジオ放送の音楽等の曲調が変化し、かえって聴感上の音質が低下するという課題があった。 High-frequency components of an audio signal extracted from a radio broadcast reception signal are affected not only by noise, but also by information originally included in the audio signal, thermal noise inside the receiver, and the like. For this reason, in the prior art disclosed in Patent Document 1, in which the attenuation amount of the high frequency component is controlled according to the detection result of the high frequency level, the attenuation amount is appropriate for the frequency characteristics of the original audio signal. may not be controlled by In this case, there is a problem that the melody of music, etc., of the radio broadcast changes, and the sound quality on the sense of hearing deteriorates.

本開示は、上述した従来の事情に鑑みて案出され、音質への影響を抑制しながらノイズを低減するハイカット処理を実現可能な受信装置及び受信方法を提供することを目的とする。 The present disclosure has been devised in view of the conventional circumstances described above, and aims to provide a receiving apparatus and a receiving method capable of implementing high-cut processing that reduces noise while suppressing the effects on sound quality.

本開示は、音声信号が含まれる放送信号を受信して受信信号のベースバンド信号を取得する受信部と、前記ベースバンド信号を復調して音声信号を取得する復調部と、前記ベースバンド信号の周波数帯域における中域成分のレベルを検出する中域検出部と、前記ベースバンド信号の周波数帯域における高域成分のレベルを検出する高域検出部と、前記中域成分のレベルと前記高域成分のレベルとのレベル差に基づいてハイカット処理の効果量を設定する処理部と、前記設定したハイカット処理の効果量に従って前記音声信号のハイカット処理を行うハイカットフィルタ部と、を備える受信装置を提供する。 The present disclosure includes a receiving unit that receives a broadcast signal including an audio signal and obtains a baseband signal of the received signal, a demodulator that demodulates the baseband signal to obtain an audio signal, and the baseband signal. a mid-range detector that detects the level of the mid-range component in the frequency band; a high-range detector that detects the level of the high-range component in the frequency band of the baseband signal; and the level of the mid-range component and the high-range component. and a high-cut filter unit for performing high-cut processing on the audio signal according to the set effect amount of high-cut processing. .

また、本開示は、音声信号が含まれる放送信号を受信する受信装置における受信方法であって、前記放送信号を受信して受信信号のベースバンド信号を取得し、前記ベースバンド信号を復調して音声信号を取得し、前記ベースバンド信号の周波数帯域における中域成分のレベルを検出し、前記ベースバンド信号の周波数帯域における高域成分のレベルを検出し、処理部により、前記中域成分のレベルと前記高域成分のレベルとのレベル差に基づいてハイカット処理の効果量を設定し、前記設定したハイカット処理の効果量に従ってハイカットフィルタ部において前記音声信号のハイカット処理を行う、受信方法を提供する。 Further, the present disclosure is a reception method in a receiving device that receives a broadcast signal including an audio signal, which receives the broadcast signal, obtains a baseband signal of the received signal, demodulates the baseband signal, and demodulates the baseband signal. an audio signal is acquired, a level of a mid-range component in the frequency band of the baseband signal is detected, a level of a high-range component in the frequency band of the baseband signal is detected, and a processing unit detects the level of the mid-range component and the level of the high-frequency component, setting an effect amount of high-cut processing based on the level difference, and performing high-cut processing of the audio signal in a high-cut filter unit according to the set effect amount of high-cut processing. .

本開示によれば、音質への影響を抑制しながらノイズを低減するハイカット処理を実現できる。 According to the present disclosure, it is possible to implement high-cut processing that reduces noise while suppressing the impact on sound quality.

実施の形態に係る受信装置の構成の一例を示すブロック図A block diagram showing an example of a configuration of a receiving device according to an embodiment 実施の形態における中域検出部及び高域検出部による通過特性の一例を示す特性図FIG. 4 is a characteristic diagram showing an example of pass characteristics of the mid-range detection section and the high-range detection section according to the embodiment; 実施の形態に係るハイカット処理の動作を説明するためのフローチャートFlowchart for explaining the operation of high-cut processing according to the embodiment 実施の形態に係るハイカット処理の効果量の設定の一例を示す特性図FIG. 4 is a characteristic diagram showing an example of setting the effect amount of high-cut processing according to the embodiment; 音声信号が中域型の曲調の場合のハイカット処理の一例を示す特性図Characteristic diagram showing an example of high-cut processing when the audio signal has a mid-range melody 音声信号が高域型の曲調の場合のハイカット処理の一例を示す特性図Characteristic diagram showing an example of high-cut processing when the audio signal has a high-frequency melody

以下、適宜図面を適宜参照しながら、本開示に係る受信装置及び受信方法を具体的に開示した実施の形態を詳細に説明する。但し、必要以上に詳細な説明は省略する場合がある。例えば、既によく知られた事項の詳細説明や実質的に同一の構成に対する重複説明を省略する場合がある。これは、以下の説明が不必要に冗長になることを避け、当業者の理解を容易にするためである。なお、添付図面及び以下の説明は、当業者が本開示を十分に理解するために提供されるものであって、これらにより特許請求の範囲に記載の主題を限定することは意図されていない。 Hereinafter, embodiments specifically disclosing a receiving apparatus and a receiving method according to the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art. It should be noted that the accompanying drawings and the following description are provided to allow those skilled in the art to fully understand the present disclosure and are not intended to limit the claimed subject matter.

(実施の形態)
本実施の形態では、本開示に係る受信装置及び受信方法の一例として、FM放送受信用のラジオ受信機に適用した構成例について説明する。
(Embodiment)
In the present embodiment, as an example of the receiving apparatus and receiving method according to the present disclosure, a configuration example applied to a radio receiver for receiving FM broadcast will be described.

なお、以下の説明では、受信装置をFM放送受信用のラジオ受信機に適用する例を説明するが、これに限定されるものではなく、AM放送受信用のラジオ受信機に適用してもよい。また、車載型、据え置き型、携帯型等の各種受信装置に適用可能である。 In the following description, an example in which the receiving device is applied to a radio receiver for receiving FM broadcasts will be described, but the present invention is not limited to this, and may be applied to a radio receiver for receiving AM broadcasts. . In addition, it can be applied to various types of receivers such as in-vehicle type, stationary type, and portable type.

図1は、実施の形態に係る受信装置の構成の一例を示すブロック図である。受信装置は、主に、処理部11、アンテナ12、受信部13、復調部14、ハイカットフィルタ部15、オーディオアンプ16、スピーカ17、ノイズ検出部18、変調度検出部19、受信電界強度検出部20、中域検出部21、及び高域検出部22を有して構成される。 FIG. 1 is a block diagram showing an example of the configuration of a receiving device according to an embodiment. The receiving device mainly includes a processing unit 11, an antenna 12, a receiving unit 13, a demodulating unit 14, a high cut filter unit 15, an audio amplifier 16, a speaker 17, a noise detecting unit 18, a modulation degree detecting unit 19, and a received electric field strength detecting unit. 20 , a mid-range detector 21 , and a high-range detector 22 .

処理部11は、CPU(Central Processing Unit)、FPGA(Field Programmable Gate Array)、DSP(Digital Signal Processor)等のプロセッサによって構成され、受信装置の各部の動作に関する処理を実行する。処理部11は、図示しないメモリに記憶されたプログラムに従って動作するものであってもよいし、ハードウェアによりその一部又は全部の機能を実現するものであってもよい。処理部11は、ハイカットフィルタ部15によるハイカット処理を制御する機能を有する。 The processing unit 11 is configured by a processor such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor), etc., and executes processing related to the operation of each unit of the receiving apparatus. The processing unit 11 may operate according to a program stored in a memory (not shown), or may implement some or all of its functions by hardware. The processing section 11 has a function of controlling high-cut processing by the high-cut filter section 15 .

アンテナ12は、放送波等の無線信号を受信するためのアンテナであり、例えば、アンテナ12には、FMラジオ放送の無線信号が誘起する。受信部13は、アンテナ12にて受波した高周波の無線信号の周波数変換等を行い、FM放送信号から希望チャンネルのべーバンド信号を抽出する。例えば、受信部13は、アンテナ12に誘起した無線周波数帯のFM放送信号から所定チャンネルのFM放送信号を抽出し、ベースバンドのコンポジット信号を得る。受信部13は、コンポジット信号を復調部14に出力する。 The antenna 12 is an antenna for receiving radio signals such as broadcast waves. For example, radio signals of FM radio broadcasting are induced in the antenna 12 . The receiving unit 13 performs frequency conversion and the like on the high-frequency radio signal received by the antenna 12, and extracts a beband signal of a desired channel from the FM broadcast signal. For example, the receiver 13 extracts the FM broadcast signal of a predetermined channel from the radio frequency band FM broadcast signal induced in the antenna 12 to obtain a baseband composite signal. The receiver 13 outputs the composite signal to the demodulator 14 .

復調部14は、FM放送受信時に、L+R信号、L-R信号を含むコンポジット信号を復調する。例えば、復調部14は、コンポジット信号に対する復調を行って、ステレオ信号の音声信号を復元するように構成されている。復調部14は、復元したステレオの音声信号をハイカットフィルタ部15に出力する。なお、FM放送信号がモノラルの音声信号を伝送するものである場合には、復調部14は、モノラルの音声信号を復元してハイカットフィルタ部15に出力する。すなわち、復調部14は、復調したベースバンドの音声信号をハイカットフィルタ部15に出力するように構成されている。 The demodulator 14 demodulates the composite signal including the L+R signal and the LR signal when receiving the FM broadcast. For example, the demodulator 14 is configured to demodulate the composite signal to restore the audio signal of the stereo signal. The demodulator 14 outputs the restored stereo audio signal to the high-cut filter 15 . When the FM broadcast signal transmits a monaural audio signal, the demodulator 14 restores the monaural audio signal and outputs it to the high-cut filter 15 . That is, the demodulator 14 is configured to output the demodulated baseband audio signal to the high-cut filter 15 .

ハイカットフィルタ部15は、例えば、音声信号の高域成分を減衰させるハイカットフィルタ(図示略)と、ハイカットフィルタの減衰量を制御する制御部(図示略)とを有する。ハイカットフィルタ部15は、処理部11によりハイカットフィルタの減衰量が指示され、入力された音声信号の高域成分を所定の減衰量によって減衰させてオーディオアンプ16に出力する。 The high-cut filter section 15 has, for example, a high-cut filter (not shown) that attenuates high-frequency components of an audio signal, and a control section (not shown) that controls the amount of attenuation of the high-cut filter. The processing unit 11 instructs the high-cut filter unit 15 to attenuate the high-frequency component of the input audio signal by a predetermined attenuation amount, and outputs the high-frequency component to the audio amplifier 16 .

オーディオアンプ16は、ハイカットフィルタ部15からの音声信号を増幅してスピーカ17に出力する。スピーカ17は、音声出力デバイスの一例であり、入力された音声信号を音響として再生出力する。 The audio amplifier 16 amplifies the audio signal from the high cut filter section 15 and outputs it to the speaker 17 . The speaker 17 is an example of an audio output device, and reproduces and outputs an input audio signal as sound.

本実施の形態では、受信した音声信号の中域成分と高域成分との比較に基づいて音声信号の特徴、特に音声信号の曲調を判定し、判定結果に基づいてハイカット処理の効果量、すなわち、ハイカット処理による高域成分の減衰量を制御する。これにより、聴感上の音質の劣化を防止しながらノイズを低減するハイカット処理が可能となる。 In this embodiment, the characteristics of the audio signal, particularly the melody of the audio signal, are determined based on the comparison between the mid-range component and the high-frequency component of the received audio signal, and the effect amount of the high-cut processing is determined based on the determination result. , controls the amount of attenuation of high-frequency components due to high-cut processing. As a result, it is possible to perform high-cut processing that reduces noise while preventing the deterioration of the sound quality perceptually.

受信部13は、受信したFM放送信号のベースバンド信号を中域検出部21及び高域検出部22にも出力する。例えば、受信部13は、ベースバンドのコンポジット信号のうちのL+R信号を中域検出部21及び高域検出部22に出力してよい。 The receiving section 13 also outputs the received baseband signal of the FM broadcast signal to the mid-frequency detection section 21 and the high-frequency detection section 22 . For example, the receiving section 13 may output the L+R signal of the baseband composite signal to the mid-range detection section 21 and the high-range detection section 22 .

中域検出部21は、ベースバンド信号の周波数帯域における中域成分を通過させるバンドパスフィルタによって構成される。中域検出部21は、FM放送波によって伝送された音声信号の周波数帯域の中間領域の周波数成分(中域成分)を検出する。高域検出部22は、ベースバンド信号の周波数帯域における高域成分を通過させるバンドパスフィルタによって構成される。高域検出部22は、FM放送波によって伝送された音声信号の周波数帯域の高い領域の周波数成分(高域成分)を検出する。中域検出部21及び高域検出部22は、L+R信号が入力された場合には、入力されたL+R信号について中域成分及び高域成分を抽出する。 The mid-range detector 21 is configured by a bandpass filter that passes mid-range components in the frequency band of the baseband signal. The middle frequency detection unit 21 detects frequency components (middle frequency components) in the middle region of the frequency band of the audio signal transmitted by the FM broadcast wave. The high-frequency detector 22 is composed of a bandpass filter that passes high-frequency components in the frequency band of the baseband signal. The high frequency detection unit 22 detects frequency components (high frequency components) in the high frequency band of the audio signal transmitted by the FM broadcast wave. When the L+R signal is input, the mid-range detection section 21 and the high-range detection section 22 extract the mid-range component and the high-range component of the input L+R signal.

FM放送波を受信する場合、伝送されるFM放送信号の音声信号の周波数帯域は例えば約50Hz~15kHz程度であり、中域成分は約300Hz~3kHz、高域成分は約4kHz~15kHzである。この場合には、中域検出部21は、例えば、中心周波数が700Hzで通過帯域が300Hzから3kHzの中域成分を通過させるバンドパスフィルタによって構成することができる。また、高域検出部22は、例えば、中心周波数が9kHzで通過帯域が4kHzから15kHzの高域成分を通過させるバンドパスフィルタなどによって構成することができる。 When receiving FM broadcast waves, the frequency band of the audio signal of the transmitted FM broadcast signal is, for example, about 50 Hz to 15 kHz, the midrange component is about 300 Hz to 3 kHz, and the high frequency component is about 4 kHz to 15 kHz. In this case, the mid-range detector 21 can be configured by, for example, a bandpass filter that passes a mid-range component with a center frequency of 700 Hz and a passband of 300 Hz to 3 kHz. Further, the high frequency detection unit 22 can be configured by a bandpass filter or the like that passes high frequency components having a center frequency of 9 kHz and a pass band of 4 kHz to 15 kHz, for example.

図2は、実施の形態における中域検出部及び高域検出部による通過特性の一例を示す特性図である。図2では、横軸に周波数をとり縦軸にレベルをとって、中域検出部21及び高域検出部22による通過特性の一例を示している。中域検出部21は、ベースバンド信号の周波数帯域50Hz~15kHzのうち、300Hz~3kHzなどの帯域を通過させることで中域成分を検出し、検出結果を処理部11に出力する。また高域検出部22は、ベースバンド信号の周波数帯域50Hz~15kHzのうち、4kHz~15kHzの帯域を通過させることで高域成分を検出し、検出結果を処理部11に出力する。 FIG. 2 is a characteristic diagram showing an example of pass characteristics of a mid-range detection section and a high-range detection section according to the embodiment. FIG. 2 shows an example of the pass characteristics of the mid-range detection section 21 and the high-range detection section 22, with the frequency on the horizontal axis and the level on the vertical axis. The middle frequency detection unit 21 detects the middle frequency component by passing a band such as 300 Hz to 3 kHz in the frequency band of 50 Hz to 15 kHz of the baseband signal, and outputs the detection result to the processing unit 11 . Further, the high frequency detection unit 22 detects high frequency components by passing a band of 4 kHz to 15 kHz in the frequency band of 50 Hz to 15 kHz of the baseband signal, and outputs the detection result to the processing unit 11 .

ここで、音声信号の特徴として、音声信号が音楽である場合の曲調の判別を行う際の、音声信号の曲調について説明する。一般的には、例えば、クラシック音楽等の楽曲の音声信号については、中域成分のレベルが比較的高く、高域成分では周波数が高くなるほどレベルが低下する周波数特性を有する。本明細書では、このようなクラシック音楽等の楽曲の曲調を、中域型の曲調と称することとする。また、例えば、ポップス音楽等の楽曲の音声信号については、中域成分だけでなく、高域成分についても比較的高い周波数まで高いレベルが維持される周波数特性を有する。本明細書では、このようなポップス音楽等の楽曲の曲調を、高域型の曲調と称することとする。 Here, as a feature of the audio signal, the melody of the audio signal when determining the melody when the audio signal is music will be described. In general, for example, an audio signal of a piece of music such as classical music has a frequency characteristic in which the level of midrange components is relatively high, and the level of high range components decreases as the frequency increases. In this specification, the melody of a piece of music such as classical music is referred to as a middle-range melody. Further, for example, an audio signal of music such as pop music has frequency characteristics in which not only the mid-range component but also the high-range component maintains a high level up to a relatively high frequency. In this specification, the melody of music such as pop music is referred to as a high-range melody.

高域型の曲調の音声信号において、ノイズ低減のためにハイカット処理の効果量(ハイカットフィルタの減衰量)を大きくすると、高域成分の楽音成分も減衰されて、曲調が変化し、聴感上の音質が劣化することがある。一方、中域型の曲調の音声信号において、ハイカット処理の効果量が小さい場合には、高域成分において楽音成分に比べてノイズ成分の割合が大きくなり、聴感上の音質が劣化することがある。 If you increase the high-cut processing effect amount (attenuation amount of the high-cut filter) to reduce noise in an audio signal with a high-frequency melody, the musical tone component of the high-frequency component is also attenuated, and the melody changes. Sound quality may deteriorate. On the other hand, if the amount of effect of high-cut processing is small for an audio signal with a mid-range tone, the ratio of noise components in the high-frequency component becomes large compared to the musical tone component, and the perceived sound quality may be degraded. .

そこで、本実施の形態では、受信した音声信号を含むベースバンド信号における中域成分のレベルと高域成分のレベルとを比較し、その差分を求めることで、伝送される音声信号の特徴としての曲調を判定する。なお、高域型の曲調のポップス音楽と中域型の曲調のクラシック音楽とは、相互に楽曲の種別が異なることから、曲調の判別は、伝送される音声信号の楽曲の種別の判定であると言うこともできる。なお、音声信号の曲調は、音楽の楽曲の特徴に対応する曲調について例示しているが、これに限らず、アナウンス音声、その他の音響信号など、各種の音声信号の特徴を示す分類についても曲調の一つに含めてよい。 Therefore, in the present embodiment, the level of the mid-range component and the level of the high-range component in the baseband signal including the received voice signal are compared, and the difference between them is obtained. determine the tone. Since pop music with a high-range melody and classical music with a middle-range melody are different types of music, the determination of the melody is the determination of the type of music of the transmitted audio signal. You can also say Note that the melody of the audio signal is exemplified by the melody corresponding to the characteristics of the musical composition, but the melody is not limited to this, and the classification indicating the characteristics of various audio signals such as announcement voices and other acoustic signals is also possible. may be included in one of

受信したFM放送信号の曲調の判別のために、中域検出部21は、音声信号を含むベースバンド信号の中域成分の検出結果を処理部11に出力し、高域検出部22は、音声信号を含むベースバンド信号の高域成分の検出結果を処理部11に出力する。 In order to discriminate the tone of the received FM broadcast signal, the mid-range detection unit 21 outputs the detection result of the mid-range component of the baseband signal including the audio signal to the processing unit 11, and the high-range detection unit 22 outputs the voice signal. The detection result of the high frequency component of the baseband signal containing the signal is output to the processing unit 11 .

処理部11は、受信した音声信号の特徴(楽曲の曲調)を、中域成分のレベルと高域成分との差分によって判定する。例えば、処理部11は、音声信号を含むベースバンド信号において算出した中域成分と高域成分とのレベルの差を、予め設定された所定の閾値と比較する。そして、処理部11は、比較結果から、伝送される音声信号の楽曲の種別が中域型の曲調であるか(クラシック音楽に類似しているか)、高域型の曲調であるか(ポップス音楽に類似しているか)を判定する。 The processing unit 11 determines the characteristics of the received audio signal (tone of music) based on the difference between the level of the mid-range component and the high-range component. For example, the processing unit 11 compares the difference between the levels of the mid-range component and the high-range component calculated in the baseband signal including the audio signal with a preset threshold value. Then, from the comparison result, the processing unit 11 determines whether the type of music of the audio signal to be transmitted is mid-range melody (similar to classical music) or high-frequency melody (pop music). is similar to ).

中域型の曲調の場合には、伝送される音声信号の高域成分にはノイズ成分が含まれる割合が大きく、高域型の曲調の場合には、伝送される音声信号の高域成分には楽音成分が含まれる割合が大きいと考えられる。このため、処理部11は、音声信号が中域型の曲調であると判定した場合には、ハイカット処理の効果量を大きくし、高域型の曲調であると判定した場合には、ハイカット処理の効果量を小さくするように、ハイカットフィルタ部15を制御する。 In the case of mid-range melody, the high-frequency component of the transmitted audio signal contains a large proportion of noise components, and in the case of high-range melody, the high-frequency component of the transmitted audio signal is thought to contain a large proportion of musical tone components. For this reason, the processing unit 11 increases the effect amount of the high-cut processing when determining that the audio signal has a middle-range tone, and increases the effect amount of the high-cut processing when determining that the audio signal has a high-frequency tone. The high-cut filter unit 15 is controlled so as to reduce the effect amount of .

ポップス音楽等の高域型の曲調の音声信号については、高域の楽音成分のレベルが十分に高いので、ハイカット処理の効果量を小さくしても、受信装置のユーザはノイズについてはあまり気にならない。一方、クラシック音楽等の中域型の曲調の音声信号については、高域に含まれる楽音成分の割合が低いので、ハイカット処理の効果量を大きくしても高域の落ち込みがあまり感じられず、高域におけるノイズ低減による音質向上の効果が大きくなる。 For audio signals with high-frequency melody such as pop music, the level of high-frequency musical tone components is sufficiently high, so even if the effect amount of high-cut processing is reduced, the user of the receiving apparatus does not care much about noise. not. On the other hand, for audio signals with middle-range melody such as classical music, the ratio of musical tones contained in the high-frequency range is low, so even if the amount of high-cut processing is increased, the drop in the high-frequency range is not felt much. The effect of improving sound quality by reducing noise in high frequencies is increased.

例えば、処理部11は、高域成分のレベル低下が小さく、中域成分に比べてNdBの低下である場合、伝送される音声信号は高域型の曲調であると判定する。また、処理部11は、高域成分のレベル低下が大き目であり、中域成分に比べてMdBまで低下している場合、伝送される音声信号は中域型の曲調であると判定する。ここで、中域型の曲調の高域成分レベル低下量MdBは、高域型の曲調の高域成分レベル低下量NdBよりも減衰量が大きい(N<M)。また、中域成分と高域成分のレベル差を判定する所定の閾値AdBに対して、0≦N<A≦Mであるとすると、中域成分のレベルに対する高域成分のレベル低下がAdB未満であれば高域型の曲調、AdB以上であれば中域型の曲調であると判定する。なお、この曲調判定のレベル差の代表値の一例として、高域型の曲調を判定するNdBとしては例えば5dBを採用し、中域型の曲調を判定するMdBとしては例えば20dBを採用してよい。曲調判定の閾値及び代表値は、適宜設定変更可能である。 For example, the processing unit 11 determines that the transmitted audio signal has a high-frequency melody when the decrease in level of the high-frequency component is small and is N dB compared to that of the mid-frequency component. If the level of the high-frequency component has decreased significantly, and is MdB lower than that of the mid-range component, the processing unit 11 determines that the transmitted audio signal has a mid-range melody. Here, the high-frequency component level reduction amount MdB of the mid-range type melody has a larger attenuation amount than the high-frequency component level reduction amount NdB of the high-frequency type melody (N<M). Further, if 0≦N<A≦M with respect to a predetermined threshold value AdB for determining the level difference between the midrange component and the highrange component, the level decrease of the highrange component with respect to the level of the midrange component is less than AdB. If so, it is determined to be a high-frequency type melody, and if it is A dB or more, it is determined to be a middle-range melody. As an example of the representative value of the level difference for judging the melody, for example, 5 dB may be adopted as NdB for judging high-range timbre, and 20 dB may be adopted as MdB for judging middle-range timbre. . The threshold value and representative value for tone determination can be changed as appropriate.

処理部11は、音声信号の曲調に応じてハイカットフィルタ部15の減衰量を制御し、ハイカット処理の効果量を調整する。これにより、処理部11は、伝送される音声信号の高域成分にノイズ成分の割合が大きい場合には、ハイカットの効果量を大きくし、楽音成分の割合が大きい場合には、ハイカットの効果量を小さくすることで、ノイズを除去しながら音質の低下を抑制する。 The processing unit 11 controls the attenuation amount of the high cut filter unit 15 according to the tone of the audio signal, and adjusts the effect amount of the high cut processing. As a result, the processing unit 11 increases the high-cut effect amount when the ratio of noise components in the high-frequency components of the transmitted audio signal is large, and increases the high-cut effect amount when the ratio of musical tone components is large. is reduced, suppressing deterioration of sound quality while removing noise.

ここでは説明を簡略化するために、放送により伝送される音声信号の特徴が中域型の曲調(クラシック音楽)と高域型の曲調(ポップス音楽)のいずれであるかを判定してハイカット処理の効果量を制御する例を説明する。なお、上記例示した2つの曲調に限らず、その他の音声信号の場合であっても、中域成分のレベルと高域成分のレベルとのレベル差に応じて適宜ハイカット処理の効果量を制御してよい。 In order to simplify the explanation here, high-cut processing is performed by determining whether the characteristic of the audio signal transmitted by broadcasting is a mid-range melody (classical music) or a high-range melody (pop music). An example of controlling the effect amount of is described. It should be noted that the amount of effect of the high-cut processing is appropriately controlled according to the level difference between the level of the mid-range component and the level of the high-range component even in the case of other audio signals, not limited to the above-mentioned two melodies. you can

また、上述した例では、受信装置においてFM放送を受信する場合を例示したが、AM放送を受信する場合は、例えば、中域成分として300Hz~700Hzを採用し、高域成分として1kHz~4kHzを採用すればよい。この場合には、中域検出部21は、中心周波数が400Hzで300Hz~700Hzを通過帯域とするフィルタを採用し、高域検出部22は、中心周波数が2kHzで1kHz~4kHzを通過帯域とするフィルタを採用すればよい。 Further, in the above example, the case of receiving FM broadcasting in the receiving device was illustrated, but when receiving AM broadcasting, for example, 300 Hz to 700 Hz is adopted as the mid-range component and 1 kHz to 4 kHz as the high frequency component. should be adopted. In this case, the mid-range detector 21 employs a filter with a center frequency of 400 Hz and a pass band of 300 Hz to 700 Hz, and the high-range detector 22 employs a filter with a center frequency of 2 kHz and a pass band of 1 kHz to 4 kHz. A filter should be used.

また、本実施の形態の受信装置は、音声信号の曲調以外の情報を用いて、ハイカット処理を更に制御する。この制御のために、受信部13は、選択受信した所定チャンネルのFM放送信号による受信信号をノイズ検出部18、変調度検出部19、及び受信電界強度検出部20に出力する。 In addition, the receiving apparatus of the present embodiment further controls high-cut processing using information other than the melody of the audio signal. For this control, the receiving section 13 outputs the reception signal of the FM broadcast signal of the selected and received predetermined channel to the noise detecting section 18, the modulation degree detecting section 19, and the received electric field strength detecting section 20. FIG.

変調度検出部19は、受信部13により受信した受信信号の変調度を検出し、検出結果を処理部11に出力する。 The modulation detector 19 detects the modulation of the received signal received by the receiver 13 and outputs the detection result to the processor 11 .

放送局のFM変調器では、音声信号のピークで100%変調となるように変調処理が施される。収録された音声信号は過変調とならないようにリミッタアンプによってレベルが制限されてFM変調器に供給される。従って、収録された音声信号のレベル及びリミッタアンプの設定によっては、変調度が上がってダイナミックレンジが狭くなることもあり、逆に、変調度が下がってS/Nが低下することもある。 In the FM modulator of the broadcasting station, modulation processing is performed so that the peak of the audio signal is 100% modulated. The recorded audio signal is limited in level by a limiter amplifier so as not to be overmodulated and supplied to the FM modulator. Therefore, depending on the level of the recorded audio signal and the setting of the limiter amplifier, the degree of modulation may increase and the dynamic range may become narrower, and conversely, the degree of modulation may decrease and the S/N ratio may decrease.

すなわち、変調度が高いFM放送信号によって伝送された音声信号の高域成分はノイズ成分に比べて楽音成分の割合が大きいと考えられる。逆に、変調度が低いFM放送信号によって伝送された音声信号の高域成分は楽音成分に比べてノイズ成分の割合が大きいと考えられる。つまり、変調度が小さい場合には、ノイズが目立つことになる。 That is, it is considered that the high-frequency component of the audio signal transmitted by the FM broadcast signal with a high degree of modulation has a large ratio of the musical tone component compared to the noise component. Conversely, it is considered that the high-frequency component of the audio signal transmitted by the FM broadcast signal with the low degree of modulation has a large proportion of the noise component compared to the musical tone component. In other words, when the degree of modulation is small, noise is conspicuous.

そこで、本実施の形態では、受信信号の変調度を利用して、ハイカット処理を制御可能に構成している。処理部11は、変調度検出部19の出力に基づいて受信信号の変調度の高低を判定し、変調度に応じてハイカット処理の効果量を制御する。処理部11は、ハイカットフィルタ部15に対して、変調度が比較的低い場合にはノイズを抑制するために、ハイカット処理の効果量を大きくし、変調度が高くなるに連れてハイカット処理の効果量を小さくするように制御を行ってよい。 Therefore, in the present embodiment, the degree of modulation of the received signal is used to control the high-cut processing. The processing unit 11 determines whether the degree of modulation of the received signal is high or low based on the output of the degree-of-modulation detector 19, and controls the effect amount of the high-cut processing according to the degree of modulation. The processing unit 11 increases the effect amount of the high-cut processing for the high-cut filter unit 15 in order to suppress noise when the degree of modulation is relatively low, and increases the effect of the high-cut processing as the degree of modulation increases. Controls may be made to reduce the amount.

受信電界強度検出部20は、受信部13により受信した受信信号の受信電界強度を例えばCNR(キャリアノイズレシオ)により検出し、検出結果を処理部11に出力する。 The received electric field strength detection unit 20 detects the received electric field strength of the received signal received by the receiving unit 13 using, for example, CNR (Carrier Noise Ratio), and outputs the detection result to the processing unit 11 .

一般的に、受信装置は、受信電界強度が弱い場合や混信が多い場合等においては、受信装置内部の熱雑音が発生しやすくなり、この熱雑音の影響により、音声信号の高域成分のレベルが高くなることがある。 In general, receivers tend to generate thermal noise inside receivers when the reception field strength is weak or when there is a lot of interference. can be higher.

そこで、本実施の形態では、受信電界強度を利用して、ハイカット処理を制御可能に構成している。処理部11は、受信電界強度検出部20の出力に基づいて受信信号レベルの大小を判定し、受信電界強度に応じてハイカット処理の効果量を制御する。処理部11は、弱電界や混信状態の場合等のようにCNRが低下している場合には、ハイカットフィルタ部15に対して曲調に拘わらずハイカット処理の効果量を大きくするように制御を行ってよい。 Therefore, in the present embodiment, the received electric field strength is used to control the high-cut processing. The processing unit 11 determines the magnitude of the received signal level based on the output of the received electric field strength detection unit 20, and controls the effect amount of the high-cut processing according to the received electric field strength. The processing unit 11 controls the high-cut filter unit 15 so as to increase the effect amount of the high-cut processing regardless of the melody when the CNR is lowered, such as in the case of a weak electric field or interference. you can

ノイズ検出部18は、受信部13により受信したFM放送信号の受信信号に含まれるマルチパスノイズを検出し、ノイズレベルを取得する。また、ノイズ検出部18は、受信信号がAM放送信号である場合には、AM放送信号の受信信号に含まれるノイズを検出してノイズレベルを取得する。ノイズ検出部18は、取得したノイズレベルの情報を処理部11に出力する。 The noise detector 18 detects multipath noise contained in the received signal of the FM broadcast signal received by the receiver 13 and acquires the noise level. Further, when the received signal is an AM broadcast signal, the noise detector 18 detects noise included in the received AM broadcast signal to obtain a noise level. The noise detection unit 18 outputs the acquired noise level information to the processing unit 11 .

受信信号のノイズレベルが十分に小さい場合には、ハイカット処理によってノイズを除去することによる音質向上の効果またはノイズ低減の効果よりも、ハイカット処理による音質低下のリスクの方が大きくなることがある。そこで、本実施の形態では、受信信号のノイズレベルが所定の閾値よりも大きいか小さいかによって、ハイカット処理の実行を決定してもよい。 When the noise level of the received signal is sufficiently low, the risk of sound quality deterioration due to high-cut processing may be greater than the effect of sound quality improvement or noise reduction due to noise removal by high-cut processing. Therefore, in the present embodiment, execution of high-cut processing may be determined depending on whether the noise level of the received signal is higher or lower than a predetermined threshold.

この場合、処理部11は、ノイズ検出部18の出力に基づいて受信信号のノイズレベルの高低を判定し、ノイズレベルに応じてハイカット処理の効果量を制御する。処理部11は、受信信号のノイズレベルが所定の閾値を超えた場合にのみ、ハイカットフィルタ部15に対してハイカット処理を実行させるように制御を行ってよい。 In this case, the processing unit 11 determines whether the noise level of the received signal is high or low based on the output of the noise detection unit 18, and controls the effect amount of the high-cut processing according to the noise level. The processing unit 11 may control the high-cut filter unit 15 to perform high-cut processing only when the noise level of the received signal exceeds a predetermined threshold.

上記のように、処理部11は、中域検出部21の中域成分の検出結果及び高域検出部22の高域成分の検出結果に基づいて、受信した音声信号の特徴(曲調)に応じてハイカット処理の効果量を決定して、ハイカットフィルタ部15を制御する。また、処理部11は、音声信号の特徴に加えて、ノイズ検出部18のノイズ検出結果、変調度検出部19の変調度検出結果、受信電界強度検出部20の受信電界強度の検出結果のうちの少なくとも1つの検出結果に基づいて、ハイカット処理の効果量を決定し、ハイカットフィルタ部15を制御することも可能である。 As described above, based on the detection result of the mid-range component by the mid-range detection unit 21 and the detection result of the high-range component by the high-range detection unit 22, the processing unit 11 detects the characteristics (tone) of the received audio signal. determines the effect amount of the high-cut processing, and controls the high-cut filter section 15 . In addition to the characteristics of the audio signal, the processing unit 11 determines the noise detection result of the noise detection unit 18, the modulation degree detection result of the modulation degree detection unit 19, and the reception electric field strength detection result of the reception electric field strength detection unit 20. It is also possible to determine the effect amount of the high-cut processing and control the high-cut filter section 15 based on at least one detection result of .

上述したノイズ検出部18、変調度検出部19、受信電界強度検出部20、中域検出部21及び高域検出部22による検出は、例えば、所定周期ごと、或いは受信放送局(受信チャンネル)の切り替え時や放送番組が切り替わる時に実行すればよい。この場合、処理部11は、所定周期等の制御変更タイミングでハイカット処理の効果量を変更すればよい。なお、処理部11は、変調度の変化が急激な場合には、他の検出結果に拘わらず、ハイカット処理の効果量を所定期間だけ低下させる制御を行ってもよい。 Detection by the noise detection unit 18, the modulation degree detection unit 19, the reception electric field strength detection unit 20, the mid-range detection unit 21, and the high-range detection unit 22 described above is performed, for example, at predetermined intervals or at the reception broadcasting station (reception channel). It may be executed at the time of switching or when the broadcast program is switched. In this case, the processing unit 11 may change the effect amount of the high-cut processing at control change timing such as a predetermined cycle. It should be noted that the processing unit 11 may perform control to reduce the effect amount of the high-cut processing for a predetermined period regardless of other detection results when the degree of modulation changes abruptly.

次に本実施の形態の受信装置の動作について説明する。
図3は、実施の形態に係るハイカット処理の動作を説明するためのフローチャートである。
Next, the operation of the receiver according to this embodiment will be described.
FIG. 3 is a flowchart for explaining the operation of high-cut processing according to the embodiment.

受信装置の電源が投入されると、受信部13には、アンテナ12により受波した無線周波数帯のFM放送信号が入力される。受信部13は、例えばユーザの選局操作に従って、所望チャンネルのFM放送信号を選択し、ベースバンドのコンポジット信号に変換して復調部14に出力する。復調部14は、コンポジット信号を復調してL,R信号(音声信号)を復元し、ハイカットフィルタ部15に出力する。 When the receiving device is powered on, the receiver 13 receives an FM broadcast signal in a radio frequency band received by the antenna 12 . The receiver 13 selects an FM broadcast signal of a desired channel according to, for example, a user's channel selection operation, converts it into a baseband composite signal, and outputs the baseband composite signal to the demodulator 14 . The demodulator 14 demodulates the composite signal to restore the L and R signals (audio signals) and outputs them to the high-cut filter 15 .

処理部11は、ハイカット処理の効果量を決定し、ハイカットフィルタ部15に対して効果量情報を出力して指示する。ハイカットフィルタ部15は、処理部11によるハイカット処理の効果量情報を入力し、指示された効果量によって復調部14から入力された音声信号の高域成分を減衰させる。これにより、高域成分のマルチパスノイズが除去される。ハイカットフィルタ部15によりノイズが除去された音声信号は、オーディオアンプ16によって増幅された後、スピーカ17に出力される。そして、受信したFM放送信号の音声信号がスピーカ17から再生出力される。 The processing unit 11 determines the effect amount of the high-cut processing, and outputs effect amount information to the high-cut filter unit 15 to instruct it. The high-cut filter unit 15 receives the effect amount information of the high-cut processing by the processing unit 11, and attenuates the high frequency components of the audio signal input from the demodulation unit 14 according to the instructed effect amount. As a result, multipath noise of high frequency components is removed. The audio signal from which noise has been removed by the high-cut filter section 15 is amplified by the audio amplifier 16 and then output to the speaker 17 . Then, the audio signal of the received FM broadcast signal is reproduced and output from the speaker 17 .

受信装置は、ハイカット処理に関して、図3に示した各処理を実行する。受信部13において取得した音声信号を含むベースバンド信号は、中域検出部21及び高域検出部22にも供給される。中域検出部21及び高域検出部22は、ベースバンド信号における中域成分及び高域成分のレベルをそれぞれ検出し、検出結果を処理部11に出力する(ステップS1)。 The receiving device executes each process shown in FIG. 3 regarding the high-cut process. The baseband signal containing the audio signal acquired by the receiver 13 is also supplied to the mid-range detector 21 and the high-range detector 22 . The mid-range detection unit 21 and the high-range detection unit 22 respectively detect the levels of the mid-range component and the high-range component in the baseband signal, and output the detection results to the processing unit 11 (step S1).

処理部11は、中域検出部21及び高域検出部22の検出結果を用いて、中域成分と高域成分の差分、すなわち中域成分と高域成分のレベル差を算出して検出する(ステップS2)。処理部11は、音声信号を含むベースバンド信号の中域成分と高域成分のレベル差に基づき、受信した音声信号の曲調を判別する(ステップS3)。例えば、処理部11は、検出したレベル差が所定値AdB未満でNdBであるか、或いは所定値AdB以上でMdBであるかを判定する。この場合、処理部11は、レベル差がNdBである場合には、受信した音声信号の楽曲種別は高域型の曲調であり、レベル差がMdBである場合には、受信した音声信号の楽曲種別は中域型の曲調であると判定する。 The processing unit 11 uses the detection results of the mid-range detection unit 21 and the high-range detection unit 22 to calculate and detect the difference between the mid-range component and the high-range component, that is, the level difference between the mid-range component and the high-range component. (Step S2). The processing unit 11 determines the melody of the received audio signal based on the level difference between the middle frequency component and the high frequency component of the baseband signal including the audio signal (step S3). For example, the processing unit 11 determines whether the detected level difference is less than a predetermined value AdB and is NdB, or whether it is greater than or equal to a predetermined value AdB and is MdB. In this case, when the level difference is N dB, the processing unit 11 determines that the music type of the received audio signal is a high-frequency tune, and when the level difference is M dB, the music of the received audio signal is The type is determined to be a middle-range melody.

また、受信部13により受信したFM放送信号の受信信号は、ノイズ検出部18、変調度検出部19及び受信電界強度検出部20に供給される。変調度検出部19は、FM放送信号の受信信号の変調度を検出して検出結果を処理部11に出力する(ステップS4)。 Also, the reception signal of the FM broadcast signal received by the reception section 13 is supplied to the noise detection section 18 , the modulation degree detection section 19 and the received electric field strength detection section 20 . The modulation detector 19 detects the modulation of the received FM broadcast signal and outputs the detection result to the processor 11 (step S4).

受信電界強度検出部20は、FM放送信号の受信信号の受信電界強度を例えばCNRによって検出し、検出結果を処理部11に出力する(ステップS5)。例えば、受信電界強度検出部20は、受信電界レベルが弱電界である電波状態を検出し、弱電界状態の検出結果を処理部11に出力する。 The received electric field intensity detection unit 20 detects the received electric field intensity of the received signal of the FM broadcast signal by, for example, CNR, and outputs the detection result to the processing unit 11 (step S5). For example, the received electric field intensity detection unit 20 detects a radio wave state in which the received electric field level is a weak electric field, and outputs the detection result of the weak electric field state to the processing unit 11 .

ノイズ検出部18は、FM放送信号の受信信号のノイズレベルを検出し、検出結果を処理部11に出力する(ステップS6)。例えば、ノイズ検出部18は、受信信号のマルチパスノイズを検出し、所定値以上のノイズ検出結果を処理部11に出力する。 The noise detector 18 detects the noise level of the received FM broadcast signal and outputs the detection result to the processor 11 (step S6). For example, the noise detection unit 18 detects multipath noise in the received signal and outputs noise detection results of a predetermined value or more to the processing unit 11 .

処理部11は、中域検出部21及び高域検出部22により検出された中域成分と高域成分のレベル差に基づく曲調の判別結果によって、ハイカット処理の効果量を設定する。また、処理部11は、このハイカット処理の効果量を、変調度検出部19によって検出された変調度に応じて設定する。また、処理部11は、受信電界強度検出部20によるCNRの検出結果に基づいてハイカット処理の効果量を設定する。また、処理部11は、ノイズ検出部18によるノイズ検出結果に従って、ハイカット処理を行うか否かを判定する。 The processing unit 11 sets the effect amount of the high-cut processing based on the melody determination result based on the level difference between the mid-range component and the high-range component detected by the mid-range detection unit 21 and the high-range detection unit 22 . The processing unit 11 also sets the effect amount of this high-cut processing according to the degree of modulation detected by the degree-of-modulation detecting unit 19 . Further, the processing unit 11 sets the effect amount of the high-cut processing based on the CNR detection result by the received electric field strength detection unit 20 . Further, the processing unit 11 determines whether or not to perform high-cut processing according to the noise detection result by the noise detection unit 18 .

処理部11は、上記の処理結果に従って、ハイカットフィルタ部15の効果量を決定し、ハイカットフィルタ部15に効果量の指示を出力する(ステップS7)。ハイカットフィルタ部15の制御部は、処理部11によって指定された効果量が得られるようにハイカットフィルタの通過特性を制御する。こうして、ハイカットフィルタ部15において、処理部11の設定による効果量に従ってハイカット処理が行われる(ステップS8)。 The processing unit 11 determines the effect amount of the high-cut filter unit 15 according to the above processing result, and outputs an effect amount instruction to the high-cut filter unit 15 (step S7). The control section of the high-cut filter section 15 controls the pass characteristics of the high-cut filter so that the effect amount specified by the processing section 11 is obtained. Thus, in the high-cut filter section 15, high-cut processing is performed according to the amount of effect set by the processing section 11 (step S8).

図4は、実施の形態に係るハイカット処理の効果量の設定の一例を示す特性図である。図4では、横軸に変調度をとり、縦軸にハイカット処理の効果量をとって、ハイカット処理の効果量の設定例を示している。図4は中域成分と高域成分のレベル差に基づく曲調の判別結果、変調度の検出結果及び受信電界強度の検出結果に基づく、ハイカット処理の効果量の設定の一例を具体的に示すものである。なお、図4の縦軸のハイカット処理の効果量、すなわち減衰量は、デシベル表記を採用しており、効果量(減衰量)Y1~Y6は負のデシベル値であって、|Y1|>|Y2|>|Y3|>|Y4|>|Y5|>|Y6|である。つまり、特性図において、下端のY1が一番ハイカット処理の効果量が大きく、ハイカットフィルタにより高域レベルが小さく抑えられた状態であり、上端のY6が一番ハイカット処理の効果量が小さく、ハイカットフィルタにより高域レベルがあまり低下されず大きなレベルを保持した状態である。 FIG. 4 is a characteristic diagram showing an example of setting the effect amount of the high-cut processing according to the embodiment. In FIG. 4, the horizontal axis represents the degree of modulation, and the vertical axis represents the effect amount of the high-cut processing. FIG. 4 specifically shows an example of the setting of the effect amount of the high-cut processing based on the melody discrimination result based on the level difference between the mid-range component and the high-range component, the modulation degree detection result, and the reception electric field strength detection result. is. Note that the amount of effect of the high-cut processing on the vertical axis of FIG. 4, that is, the amount of attenuation, is expressed in decibels. Y2|>|Y3|>|Y4|>|Y5|>|Y6|. That is, in the characteristic diagram, Y1 at the lower end has the largest amount of high-cut processing effect, and the high-frequency level is suppressed by the high-cut filter. This is a state in which the high-frequency level is not lowered much by the filter and a large level is maintained.

図4において、実線は中域型の曲調(クラシック音楽に類似した曲調)の音声信号が受信された場合(例えば中域と高域のレベル差MdB)の特性を示し、破線は高域型の曲調(ポップス音楽に類似した曲調)の音声信号が受信された場合(例えば中域と高域のレベル差NdB、N<M)の特性を示している。 In FIG. 4, the solid line shows the characteristics when an audio signal of mid-range melody (a melody similar to classical music) is received (for example, the level difference MdB between the mid-range and high range), and the dashed line shows the characteristics of the high-range type. It shows the characteristics when an audio signal with a melody (a melody similar to pop music) is received (for example, the level difference between the middle range and the high range is N dB, N<M).

図4に示すように、中域型の曲調の音声信号を受信した場合には、高域型の曲調の音声信号を受信した場合に比べて、ハイカット処理の効果量を大きく設定する。この結果、クラシック音楽等の中域型の曲調については、ハイカット処理によってノイズを十分に除去することができ、音質を向上させることができる。一方、ポップス音楽等の高域型の曲調については、ハイカット処理の効果量を小さくすることにより、例えばドラムやシンバル等の音を含む高域成分まで、比較的高いレベルの楽音成分が減衰されることが抑制され、曲調が損なわれてしまうことがない。 As shown in FIG. 4, when an audio signal with a mid-range tone is received, the effect amount of the high-cut processing is set larger than when an audio signal with a high-frequency tone is received. As a result, noise can be sufficiently removed by high-cut processing for middle-range melody such as classical music, and the sound quality can be improved. On the other hand, for high-frequency melody such as pop music, by reducing the effect amount of high-cut processing, relatively high-level musical tones, including high-frequency components including sounds such as drums and cymbals, are attenuated. is suppressed, and the melody is not spoiled.

また、処理部11は、受信信号の変調度に応じて、ハイカット処理の効果量を設定する。例えば、処理部11は、受信信号の変調度に応じてハイカット処理の効果量を変化させる。この場合、処理部11は、変調度が低い程ハイカット処理の効果量を小さくし、変調度が高くなる程ハイカット処理の効果量を増加させるようにしてもよい。更に、処理部11は、ハイカット処理の効果量について、例えば、変調度m1,m2,m3(m1<m2<m3)を閾値として、変調度に応じた変化の割合を変更するように制御してもよい。 Also, the processing unit 11 sets the effect amount of the high-cut processing according to the degree of modulation of the received signal. For example, the processing unit 11 changes the effect amount of the high-cut processing according to the degree of modulation of the received signal. In this case, the processing unit 11 may reduce the effect amount of the high-cut processing as the degree of modulation is lower, and increase the effect amount of the high-cut processing as the degree of modulation is higher. Further, the processing unit 11 controls the amount of effect of the high-cut processing to change the rate of change according to the degree of modulation, using, for example, the degrees of modulation m1, m2, and m3 (m1<m2<m3) as thresholds. good too.

例えば、図4の例では、変調度m1以下及び変調度m3以上ではハイカット処理の効果量を一定とし、変調度m1~m2の間と変調度m2~m3の間における変化量を変化させている。この場合、例えば、中域型の曲調については、変調度m1以下の効果量はY1であり、高域型の曲調については、変調度m1以下の効果量はY2である(Y1<Y2)。また、例えば、中域型の曲調については、変調度m3以上の効果量はY5であり、高域型の曲調については、変調度m3以上の効果量はY6である(Y5<Y6)。なお、例えば、変調度m1,m2,m3としては、それぞれ変調度10,30,50を設定してもよい。 For example, in the example of FIG. 4, the effect amount of the high-cut processing is constant at the modulation degree m1 or less and the modulation degree m3 or more, and the change amount is changed between the modulation degrees m1 to m2 and the modulation degrees m2 to m3. . In this case, for example, for mid-range tone, the effect amount for modulation m1 or less is Y1, and for high-range tone, the effect amount for modulation m1 or less is Y2 (Y1<Y2). Further, for example, the effect amount of the modulation degree m3 or more is Y5 for the mid-range tone, and the effect amount of the modulation degree m3 or more is Y6 (Y5<Y6) for the high-frequency tone. For example, the modulation degrees m1, m2, and m3 may be set to 10, 30, and 50, respectively.

これにより、変調度が比較的低い場合には、ハイカット処理の効果量を大きくすることで、ノイズ成分を確実に減衰させ、変調度が比較的高い場合には、ハイカット処理の効果量を小さくすることで、楽音成分が減衰されることを抑制し、音質を向上させることができる。 As a result, when the degree of modulation is relatively low, the effect amount of the high-cut processing is increased to reliably attenuate the noise component, and when the degree of modulation is relatively high, the effect amount of the high-cut processing is decreased. As a result, it is possible to suppress the attenuation of the musical tone component and improve the sound quality.

更に、処理部11は、受信電界強度としてのCNRの値によって、CNRが所定値以下の場合にハイカット処理の効果量を一定の大きな値としてもよい。例えば、処理部11は、CNRの値がR2以下のとき、ハイカット処理の効果量を一定のY4としてもよく、CNRの値がR1(R2>R1)以下のとき、ハイカット処理の効果量を一定のY3としてもよい(Y3<Y4)。 Furthermore, the processing unit 11 may set the effect amount of the high-cut processing to a constant large value when the CNR value as the received electric field strength is equal to or less than a predetermined value. For example, when the CNR value is R2 or less, the processing unit 11 may set the high-cut processing effect amount to a constant Y4, and when the CNR value is R1 (R2>R1) or less, the high-cut processing effect amount may be constant. may be Y3 (Y3<Y4).

受信電界強度が弱電界の状態では、受信した音声信号の音質は悪く、ノイズ成分が支配的となる。このため、弱電界での受信時には、音声信号の曲調に拘わらず、ハイカット処理の効果量を所定値に維持することにより、確実にノイズを低減することができ、ノイズによる聞き苦しさを軽減する効果がある。 When the received electric field strength is weak, the sound quality of the received voice signal is poor and the noise component is dominant. For this reason, when receiving in a weak electric field, noise can be reliably reduced by maintaining the effect amount of high-cut processing at a predetermined value regardless of the melody of the audio signal, and the difficulty of hearing due to noise can be reduced. effective.

また、処理部11は、ノイズ検出部18により検出されたノイズレベルが所定の閾値よりも小さい場合には、ハイカット処理を停止するようにハイカットフィルタ部15を制御する。これにより、受信状態が良好でノイズの影響をあまり受けない環境では、ハイカット処理を行わないことで、音質が劣化することを防止することができる。 Further, the processing section 11 controls the high-cut filter section 15 to stop the high-cut processing when the noise level detected by the noise detection section 18 is smaller than a predetermined threshold. As a result, in an environment where the reception condition is good and the sound is not so affected by noise, it is possible to prevent deterioration of the sound quality by not performing the high-cut processing.

なお、処理部11によるハイカット処理の効果量の制御は、例えば、所定周期で実施する。また、変調度が急に変化する場合、例えば、曲目紹介の人の声等の変調度が比較的低い音声信号から、楽曲が開始されて変調度が比較的高い音声信号に急に切換った場合等においては、処理部11は、楽曲の曲調の判別が完了する前に、ハイカット処理の効果量を所定期間だけ所定値に低下させるように制御を行ってもよい。この結果、ハイカット処理の効果量を短時間に低下させることができ、楽曲の開始直後から過剰なハイカット処理による音質の劣化を防止することができる。 Note that the control of the effect amount of the high-cut processing by the processing unit 11 is performed, for example, at predetermined intervals. Also, when the degree of modulation suddenly changes, for example, an audio signal with a relatively low degree of modulation, such as the voice of a person introducing a piece of music, is suddenly switched to an audio signal with a relatively high degree of modulation at the start of a song. In some cases, the processing unit 11 may perform control so that the effect amount of the high-cut processing is reduced to a predetermined value for a predetermined period of time before the determination of the tone of the music is completed. As a result, the amount of effect of the high-cut processing can be reduced in a short period of time, and it is possible to prevent deterioration of sound quality due to excessive high-cut processing immediately after the start of music.

次に、本実施の形態によるハイカット処理の効果について説明する。
図5は、音声信号が中域型の曲調の場合のハイカット処理の一例を示す特性図であり、図6は、音声信号が高域型の曲調の場合のハイカット処理の一例を示す特性図である。図5及び図6は、実施の形態の効果を説明するものであり、横軸に時間をとり縦軸に周波数をとって、ハイカット処理による周波数特性の変化を示している。図5及び図6において、左側がハイカット処理前、右側がハイカット処理後のそれぞれの周波数特性を示している。
Next, the effect of the high-cut processing according to this embodiment will be described.
FIG. 5 is a characteristic diagram showing an example of high-cut processing when the audio signal has a mid-range tone, and FIG. 6 is a characteristic diagram showing an example of high-cut processing when the audio signal has a high-frequency tone. be. FIGS. 5 and 6 are for explaining the effects of the embodiment, and show changes in frequency characteristics due to high-cut processing, with time on the horizontal axis and frequency on the vertical axis. 5 and 6, the left side shows the frequency characteristics before high-cut processing, and the right side shows the frequency characteristics after high-cut processing.

図5に示す中域型の曲調では、中域成分に比べて高域成分は比較的大きく減衰しており、中域成分と高域成分のレベル差によって、処理部11は、音声信号の特徴がクラシック音楽等の中域型の曲調であると判定する。この場合には、処理部11は、ハイカット減衰量を比較的大きく設定する。これにより、図5の右側に示すように、ハイカット処理によって、高域成分は比較的大きな効果量で減衰され、高域成分に含まれるノイズが確実に除去される。なお、高域成分に含まれる楽音成分の割合は比較的小さいので、ハイカット処理によって楽音成分が受ける影響は比較的小さく、聴感上の音質は殆ど変化しない。 In the mid-range melody shown in FIG. 5, the high-frequency component is attenuated relatively more than the mid-range component. is determined to be a middle-range melody such as classical music. In this case, the processing unit 11 sets the high-cut attenuation amount to a relatively large value. As a result, as shown on the right side of FIG. 5, the high-frequency component is attenuated with a relatively large amount of effect by the high-cut processing, and noise contained in the high-frequency component is reliably removed. Since the ratio of the musical tone components contained in the high-frequency components is relatively small, the effect of the high-cut processing on the musical tone components is relatively small, and the perceived sound quality hardly changes.

図6に示す高域型の曲調では、中域成分と同様に高域成分においてもレベルが比較的高い周波数まで維持される。処理部11は、中域成分と高域成分のレベル差によって、ポップス音楽等の高域型の曲調であると判定する。この場合には、処理部11は、ハイカット減衰量を比較的小さく設定する。これにより、図6の右側に示すように、高域成分のハイカット処理の効果量は比較的小さく、高域成分に含まれる楽音成分の減衰が抑制される。この結果、ハイカット処理が行われたとしても、高域成分の楽音成分が受ける影響は比較的小さく、聴感上の音質は殆ど変化しない。なお、高域成分は楽音成分の割合が高いので、多少ノイズが残っていたとしても、楽音成分によってノイズは目立たない。 In the high-range melody shown in FIG. 6, the level of the high-range component is maintained up to relatively high frequencies in the same way as the mid-range component. The processing unit 11 determines that the tone is of a high frequency type, such as pop music, based on the level difference between the middle frequency component and the high frequency component. In this case, the processing unit 11 sets the high cut attenuation amount to a relatively small value. As a result, as shown on the right side of FIG. 6, the amount of effect of the high-cut processing on the high-frequency components is relatively small, and the attenuation of the tone components contained in the high-frequency components is suppressed. As a result, even if the high-cut processing is performed, the influence of the musical tone components in the high frequency range is relatively small, and the perceived sound quality hardly changes. Since the high-frequency component has a high proportion of musical tone components, even if some noise remains, the noise is not conspicuous due to the musical tone component.

このように、本実施の形態では、受信信号のベースバンド音声信号の中域成分のレベルと高域成分のレベルとのレベル差に応じてハイカット処理の減衰量を調整している。これによって、伝送される音声信号の特徴(楽曲の曲調)を損なうことなく、ノイズの低減処理が可能であり、効果的なノイズ除去を行うことができる。 As described above, in the present embodiment, the attenuation amount of the high-cut processing is adjusted according to the level difference between the level of the mid-range component and the level of the high-range component of the baseband audio signal of the received signal. As a result, noise reduction processing can be performed without impairing the characteristics of the audio signal to be transmitted (tone of music), and effective noise removal can be performed.

以上のように、本実施の形態の受信装置は、受信部13において音声信号が含まれる放送信号を受信して受信信号のベースバンド信号を取得し、復調部14においてベースバンド信号を復調して音声信号を取得する。中域検出部21は、ベースバンド信号の周波数帯域における中域成分のレベルを検出し、高域検出部22は、ベースバンド信号の周波数帯域における高域成分のレベルを検出する。処理部11は、中域成分のレベルと高域成分のレベルとのレベル差に基づいてハイカット処理の効果量を設定する。ハイカットフィルタ部15は、処理部11にて設定したハイカット処理の効果量に従って復調された音声信号のハイカット処理を行う。 As described above, in the receiving apparatus of the present embodiment, the receiving unit 13 receives a broadcast signal containing an audio signal, acquires the baseband signal of the received signal, and the demodulating unit 14 demodulates the baseband signal. Acquire an audio signal. The middle band detector 21 detects the level of the middle band component in the frequency band of the baseband signal, and the high band detector 22 detects the level of the high band component in the frequency band of the baseband signal. The processing unit 11 sets the effect amount of the high-cut processing based on the level difference between the level of the mid-range component and the level of the high-range component. The high-cut filter unit 15 performs high-cut processing on the demodulated audio signal according to the high-cut processing effect amount set by the processing unit 11 .

これにより、音声信号に対するハイカット処理の効果量は、ベースバンド信号の中域成分のレベルと高域成分のレベルとのレベル差に対応したものとなる。このレベル差は、ラジオ放送において伝送される音声信号の特徴、例えば楽曲の曲調を表しており、ハイカット処理は音声信号の特徴に応じて効果量が設定されることになる。これにより、曲調に応じて必要な高域成分の減衰を抑制しながらノイズ除去が可能であり、受信信号の再生信号として、曲調を維持し音質を向上させた音声信号を得ることができる。 As a result, the amount of effect of the high-cut processing on the audio signal corresponds to the level difference between the level of the mid-range component and the level of the high-range component of the baseband signal. This level difference represents the characteristics of the audio signal transmitted in the radio broadcast, for example, the melody of the music, and the effect amount of the high-cut processing is set according to the characteristics of the audio signal. As a result, it is possible to remove noise while suppressing the attenuation of the high-frequency components necessary according to the tune, and to obtain an audio signal with improved sound quality while maintaining the tune as a reproduction signal of the received signal.

また、本実施の形態の受信装置では、処理部11は、中域成分と高域成分のレベル差が所定値より小さい場合にハイカット処理の効果量を小さくし、レベル差が所定値より大きい場合にハイカット処理の効果量を大きくする。これにより、中域成分のレベルに比べて高域成分のレベルが低い中域型の曲調の楽曲については、ハイカット処理の効果量が大きくなり、ノイズを効果的に除去できる。また、この場合には高域成分の楽音成分の割合が小さいので、音質に与える影響は小さい。一方、中域成分のレベルと同様に高域成分のレベルも高い高域型の曲調の楽曲については、ハイカット処理の効果量が小さくなり、高域成分の楽音成分が減衰されることを抑制できる。また、この場合には高域成分の楽音成分によってノイズは目立たない。こうして、音声信号の特徴(楽曲の曲調)に応じたノイズ除去動作が可能となる。 Further, in the receiving apparatus of the present embodiment, the processing unit 11 reduces the effect amount of the high-cut processing when the level difference between the mid-range component and the high-frequency component is smaller than a predetermined value, and when the level difference is larger than the predetermined value increase the effect amount of the high-cut processing. As a result, the amount of effect of the high-cut processing is increased for music with a middle-range tone in which the level of the high-frequency component is lower than the level of the middle-range component, and noise can be effectively removed. Also, in this case, since the ratio of the musical tone component of the high frequency component is small, the effect on the sound quality is small. On the other hand, for songs with high-frequency melody in which the level of the high-frequency component is high as well as the level of the mid-frequency component, the amount of effect of the high-cut processing becomes small, and it is possible to suppress the attenuation of the musical tone component of the high-frequency component. . Also, in this case, the noise is not conspicuous due to the musical tone component of the high frequency component. In this way, it is possible to perform a noise removal operation in accordance with the characteristics of the audio signal (tone of music).

また、本実施の形態の受信装置では、受信信号の変調度を検出する変調度検出部19を有し、処理部11は、変調度に基づいてハイカット処理の効果量を設定する。処理部11は、例えば変調度に基づいてハイカット処理の効果量を変化させ、変調度が所定値より大きい場合にハイカット処理の効果量を小さくし、変調度が所定値より小さい場合にハイカット処理の効果量を大きくする。これにより、変調度が小さくノイズが目立つ音声信号については、ハイカット処理の効果量を大きくすることで、ノイズを確実に除去できる。一方、変調度が大きくノイズの割合が小さい音声信号については、ハイカット処理の効果量を小さくすることで、ハイカット処理により楽音成分が減衰してしまうことを抑制し、音質を向上させることができる。 Further, the receiving apparatus of the present embodiment has a modulation degree detector 19 that detects the degree of modulation of the received signal, and the processing unit 11 sets the effect amount of the high-cut processing based on the degree of modulation. For example, the processing unit 11 changes the effect amount of the high-cut processing based on the degree of modulation, reduces the effect amount of the high-cut processing when the degree of modulation is greater than a predetermined value, and reduces the effect amount of the high-cut processing when the degree of modulation is less than the predetermined value. Increase effect size. As a result, noise can be reliably removed from an audio signal having a small degree of modulation and conspicuous noise by increasing the effect amount of the high-cut processing. On the other hand, for an audio signal with a large degree of modulation and a small noise ratio, by reducing the effect amount of the high-cut processing, it is possible to suppress the attenuation of the musical tone component by the high-cut processing and improve the sound quality.

また、本実施の形態の受信装置では、受信信号の受信電界強度を検出する受信電界強度検出部20を有し、処理部11は、受信電界強度が所定値よりも小さい場合にハイカット処理の効果量を大きくする。処理部11は、受信電界強度が所定値よりも小さい場合にハイカット処理の効果量を所定の一定値に設定して維持する。これにより、弱電界時には強制的に所定の効果量でハイカット処理を行うことによって、出力する音声信号におけるノイズレベルを抑制でき、受信環境が良くない場合の聞き苦しさを軽減できる。 Further, the receiving apparatus of the present embodiment has a reception electric field strength detection unit 20 that detects the reception electric field strength of the received signal, and the processing unit 11 detects the effect of the high-cut processing when the reception electric field strength is smaller than a predetermined value. Increase quantity. The processing unit 11 sets and maintains the effect amount of the high-cut processing at a predetermined constant value when the received electric field strength is smaller than a predetermined value. As a result, by forcibly performing high-cut processing with a predetermined amount of effect when the electric field is weak, the noise level in the output audio signal can be suppressed, and the difficulty of hearing can be reduced when the reception environment is not good.

また、本実施の形態の受信装置では、受信信号のノイズレベルを検出するノイズ検出部18を有し、処理部11は、ノイズレベルが所定値よりも小さい場合にハイカット処理を停止させる。これにより、ノイズレベルが十分に低い場合には、ノイズを低減する必要がない場合があり、この場合にハイカット処理を行わないようにすることで、音声信号における楽音成分の減衰により音質が劣化することを抑制できる。 Further, the receiving apparatus of the present embodiment has noise detection section 18 for detecting the noise level of the received signal, and processing section 11 stops high-cut processing when the noise level is lower than a predetermined value. As a result, if the noise level is sufficiently low, it may not be necessary to reduce noise. can be suppressed.

また、本実施の形態の受信方法は、音声信号が含まれる放送信号を受信する受信装置における受信方法であって、受信部13により放送信号を受信して受信信号のベースバンド信号を取得し、復調部14によりベースバンド信号を復調して音声信号を取得する。また、中域検出部21によりベースバンド信号の周波数帯域における中域成分のレベルを検出し、高域検出部22によりベースバンド信号の周波数帯域における高域成分のレベルを検出する。また、処理部11により、中域成分のレベルと高域成分のレベルとのレベル差に基づいてハイカット処理の効果量を設定し、設定したハイカット処理の効果量に従ってハイカットフィルタ部15において音声信号のハイカット処理を行う。これにより、音声信号の特徴に応じたハイカット処理を実行でき、音質への影響を抑制しながらノイズを低減することができ、音質劣化を抑制した音声信号を再生出力することができる。 Further, the receiving method of the present embodiment is a receiving method in a receiving device that receives a broadcast signal including an audio signal, and the receiving unit 13 receives the broadcast signal to obtain a baseband signal of the received signal, A demodulation unit 14 demodulates the baseband signal to obtain an audio signal. In addition, the mid-range detector 21 detects the level of the mid-range component in the frequency band of the baseband signal, and the high-range detector 22 detects the level of the high-range component in the frequency band of the baseband signal. Further, the processing unit 11 sets the effect amount of the high-cut processing based on the level difference between the level of the mid-frequency component and the level of the high-frequency component, and the high-cut filter unit 15 processes the audio signal according to the set effect amount of the high-cut processing. Perform high-cut processing. As a result, it is possible to perform high-cut processing according to the characteristics of the audio signal, reduce noise while suppressing the effect on sound quality, and reproduce and output the audio signal with reduced sound quality deterioration.

以上、図面を参照しながら各種の実施の形態について説明したが、本発明はかかる例に限定されないことは言うまでもない。当業者であれば、特許請求の範囲に記載された範疇内において、各種の変更例、修正例、置換例、付加例、削除例、均等例に想到し得ることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。また、発明の趣旨を逸脱しない範囲において、上述した実施の形態における各構成要素を任意に組み合わせてもよい。 Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is obvious that a person skilled in the art can conceive of various modifications, modifications, substitutions, additions, deletions, and equivalents within the scope of the claims. Naturally, it is understood that it belongs to the technical scope of the present invention. Also, the components in the above-described embodiments may be combined arbitrarily without departing from the spirit of the invention.

本開示は、音質への影響を抑制しながらノイズを低減するハイカット処理を実現可能な受信装置及び受信方法として有用である。 INDUSTRIAL APPLICABILITY The present disclosure is useful as a receiving device and a receiving method capable of realizing high-cut processing that reduces noise while suppressing effects on sound quality.

11 処理部
12 アンテナ
13 受信部
14 復調部
15 ハイカットフィルタ部
16 オーディオアンプ
17 スピーカ
18 ノイズ検出部
19 変調度検出部
20 受信電界強度検出部
21 中域検出部
22 高域検出部
11 Processing Unit 12 Antenna 13 Receiving Unit 14 Demodulator 15 High Cut Filter 16 Audio Amplifier 17 Speaker 18 Noise Detector 19 Modulation Detector 20 Received Electric Field Strength Detector 21 Middle Range Detector 22 High Range Detector

Claims (8)

音声信号が含まれる放送信号を受信して受信信号のベースバンド信号を取得する受信部と、
前記ベースバンド信号を復調して音声信号を取得する復調部と、
前記ベースバンド信号の周波数帯域における中域成分のレベルを検出する中域検出部と、
前記ベースバンド信号の周波数帯域における高域成分のレベルを検出する高域検出部と、
前記受信信号のキャリアノイズレシオを検出する受信電界強度検出部と、
前記音声信号のハイカット処理の効果量を設定する処理部と、
前記設定したハイカット処理の効果量に従って前記音声信号のハイカット処理を行うハイカットフィルタ部と、を備え、
前記処理部は、前記キャリアノイズレシオが所定値以下の場合に前記効果量を所定の一定値に設定し、前記キャリアノイズレシオが前記所定値よりも大きい場合、前記中域成分のレベルと前記高域成分のレベルとのレベル差に基づいて前記効果量を設定する、
受信装置。
a receiver that receives a broadcast signal containing an audio signal and obtains a baseband signal of the received signal;
a demodulator that demodulates the baseband signal to obtain an audio signal;
a midrange detector that detects the level of midrange components in the frequency band of the baseband signal;
a high frequency detection unit that detects the level of high frequency components in the frequency band of the baseband signal;
a reception electric field intensity detection unit that detects a carrier noise ratio of the reception signal;
Saidof the audio signala processing unit for setting an effect amount of high-cut processing;
a high-cut filter unit that performs high-cut processing on the audio signal according to the set effect amount of the high-cut processing;with
The processing unit sets the effect amount to a predetermined constant value when the carrier noise ratio is equal to or less than a predetermined value, and sets the effect amount to a predetermined constant value when the carrier noise ratio is greater than the predetermined value. setting the effect amount based on the level difference from the level of the range component;
receiving device.
請求項1に記載の受信装置であって、
前記処理部は、前記レベル差が所定値より小さい場合に前記効果量を小さくする、受信装置。
The receiving device according to claim 1,
The receiving device, wherein the processing unit reduces the effect amount when the level difference is smaller than a predetermined value.
請求項1に記載の受信装置であって、
前記処理部は、前記レベル差が所定値より大きい場合に前記効果量を大きくする、受信装置。
The receiving device according to claim 1,
The receiving device, wherein the processing unit increases the effect amount when the level difference is greater than a predetermined value.
請求項1に記載の受信装置であって、
前記受信信号の変調度を検出する変調度検出部を有し、
前記処理部は、
前記変調度に基づいて前記効果量を設定する、受信装置。
The receiving device according to claim 1,
Having a modulation degree detection unit that detects the degree of modulation of the received signal,
The processing unit is
A receiving device that sets the effect amount based on the degree of modulation.
請求項4に記載の受信装置であって、
前記処理部は、前記変調度が所定値より大きい場合に前記効果量を小さくする、受信装置。
The receiving device according to claim 4,
The receiving device, wherein the processing unit reduces the effect amount when the degree of modulation is greater than a predetermined value.
請求項4に記載の受信装置であって、
前記処理部は、前記変調度が所定値より小さい場合に前記効果量を大きくする、受信装置。
The receiving device according to claim 4,
The receiving device, wherein the processing unit increases the effect amount when the degree of modulation is smaller than a predetermined value.
請求項1に記載の受信装置であって、
前記受信信号のノイズレベルを検出するノイズ検出部を有し、
前記処理部は、前記ノイズレベルが所定値よりも小さい場合に前記ハイカット処理を停止させる、受信装置。
The receiving device according to claim 1,
Having a noise detection unit that detects the noise level of the received signal,
The receiving device, wherein the processing unit stops the high-cut processing when the noise level is smaller than a predetermined value.
音声信号が含まれる放送信号を受信する受信装置における受信方法であって、
前記放送信号を受信して受信信号のベースバンド信号を取得し、
前記ベースバンド信号を復調して音声信号を取得し、
前記ベースバンド信号の周波数帯域における中域成分のレベルを検出し、
前記ベースバンド信号の周波数帯域における高域成分のレベルを検出し、
前記受信信号のキャリアノイズレシオを検出し、
処理部により、前記音声信号のハイカット処理の効果量を設定し、
前記設定したハイカット処理の効果量に従ってハイカットフィルタ部において前記音声信号のハイカット処理を行
前記処理部は、前記キャリアノイズレシオが所定値以下の場合に前記効果量を所定の一定値に設定し、前記キャリアノイズレシオが前記所定値よりも大きい場合、前記中域成分のレベルと前記高域成分のレベルとのレベル差に基づいて前記効果量を設定する、
受信方法。
A reception method in a receiving device for receiving a broadcast signal containing an audio signal,
receiving the broadcast signal to obtain a baseband signal of the received signal;
demodulating the baseband signal to obtain an audio signal;
detecting the level of a midrange component in the frequency band of the baseband signal;
detecting the level of high frequency components in the frequency band of the baseband signal;
detecting a carrier noise ratio of the received signal;
By the processing unit,of the audio signalSet the effect amount of high cut processing,
High-cut processing of the audio signal is performed in the high-cut filter section according to the set effect amount of the high-cut processing.stomach,
The processing unit sets the effect amount to a predetermined constant value when the carrier noise ratio is equal to or less than a predetermined value, and sets the effect amount to a predetermined constant value when the carrier noise ratio is greater than the predetermined value. setting the effect amount based on the level difference from the level of the range component;
receiving method.
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